Drain tanks are kitchen apparatus commonly used in home kitchens for washing and draining dishes. The existing drain tanks are designed with steps on an inner wall of the tank for the placement of a drain rack, but in order to meet consumers' desire for adjustable height, in the prior art, the height of the drain rack is configured to be adjustable by providing a plurality of steps in the drain tank at different heights. However, regarding this technical solution, as the result of providing steps at different heights, the distance between the inner walls of the drain tank decreases as the height of the steps decreases, and therefore the width dimension of the drain rack also needs to be adjusted according to the distance between the inner walls of the drain tank, so that a plurality of drain racks are required, thereby increasing the production costs. Moreover, the bottom operation space of the drain tank is compressed, which is inconvenient for the washing operation of the washer.